William R. Jacobs, Jr., Ph.D.In this ambitious project, Dr. Jacobs and colleagues will “knock out” every gene of Mycobacterium tuberculosis (MTB), the bacterium that causes TB. By knocking out or deleting a gene, researchers can determine the gene’s function by observing how loss of that gene affects the organism. It is already known that certain MTB genes are crucial for the bacterium’s survival — helping it resist antibiotics, for example, and enabling it to ward off the immune system of the host.

The researchers will use a technique called specialized transduction (developed in the Jacobs lab) to generate approximately 4,500 specialized transducing phages. These phages will then be used to knock out every gene present in three different MTB strains, including the newly evolved extensively drug resistant (XDR-TB) strain.

Deletion libraries will be built in two different genetic backgrounds: H37Rv, the standard disease-causing laboratory strain; and mc26320, a nonpathogenic derivative of H37Rv. Since H37Rv is a pathogen, it must be studied under secure BSL3 laboratory conditions; by contrast, mc26320, an important strain used for vaccine studies, requires the less stringent BSL2 containment. The findings from this project will be made available to all qualified researchers worldwide via an NIH-designated depository and distribution center.

“TB strains that resist some, most or even all current chemotherapies are becoming increasingly common,” said Dr. Jacobs. “We hope that our systematic evaluation of the entire TB genome will reveal genetic vulnerabilities that we can target with new and more effective treatments and vaccines.”

The Jacobs consortium includes researchers from the Genomics Institute of the Novartis Research Foundation (GNF), the University of Pittsburgh, Johns Hopkins University and the new KwaZulu-Natal Research Institute for TB-HIV (K-RITH Institute) at the University of KwaZulu-Natal in South Africa.